For reasons still unknown, the brain neurotransmitter serotonin is critical to the development and treatment of depression and chronic anxiety. An even a bigger mystery is why more women than men are affected by depression and chronic anxiety.

Hristina Jovanovic, Swedish medical university Karolinska Institute, believes he may be able to show why women are affected by depression and chronic anxiety. Using a PET scanner he was able to show that men and women differ in the number of binding sites for serotonin in certain parts of the brain.